In 1882, the bishop of Barcelona laid the cornerstone of what would become the city’s top tourist attraction – a soaring church in the flamboyant Catalan modernisme style, a local version of nature-driven art nouveau. Its 18 slender towers soar above the Spanish city’s skyline, beaten in height only by Montjuïc, the hill that supplied much of their stone. But 140 years later, they remain incomplete, the construction of the Expiatory Temple of the Holy Family, or Sagrada Família, persistently dogged by delays. Its first architect, Francesc del Villar, resigned after little more than a year. Its second, Antoni Gaudí , repeatedly revised the design even while construction continued, until he was run over by a tram in 1926. His replacement of del Villar’s modest and humdrum neo-Gothic church with something revolutionary in both its design and engineering, to be, at 172.5 metres (566 feet), the tallest church in the world did nothing to speed things up. During the 1936–39 Spanish civil war, anarchists torched Gaudí’s models and designs, which left his disciples subsequently doubling as both detectives and architects, piecing together the master’s intentions from what remained and scouring previously published plans and newspaper articles. But the more of Gaudí’s improbable but inspirational creation appeared above ground, the more the world took notice. Its Unesco World Heritage listing in 2005 gave it global publicity and by 2019, visitor numbers to the partly constructed temple were approaching five million each year, their entrance fees funding an acceleration in construction. It was finally announced that, although work on the highly decorated facades would continue well into the future, the building would be declared structurally complete in 2026, the centenary of Gaudí’s death. And then along came Covid-19 . In March 2020, construction came to a halt, and tourism dried up. The project had been privately financed by the pious since its inception, but the revenue essential to funding further progress had evaporated. When work resumed in October that year, the decision was taken to concentrate on completion of the Mary tower – the second-highest. On December 8, after a day of ceremonies that will be watchable online (at estel.sagradafamilia.org ) , the giant, 12-pointed, internally illuminated star of glass and steel hoisted up in November to top the tower will be switched on, inaugurating celebrations that will last until January 4. Visitors are already returning, although the throngs in the forest-like nave (the central part of a church) are still well under half what they once were. All heads crane upwards to follow the lines of leaning pillars in porphyry, basalt or granite. These tilt not because they self-consciously rebel against tradition, as 19th-century art nouveau generally did, but because they form the lower ends of catenary arches. A catenary is the arc formed by a rope or chain when left to hang freely, naturally distributing tension equally along its length. Gaudí took 10 years to produce an upside-down model of the church entirely made from hanging ropes, each weighted with bags of shot to replicate the stresses arising from the weight of the materials that he would use. A mirror placed beneath his model showed what the building would look like when the tensions of the hanging ropes were inverted and replaced with the equally distributed compression of leaping columns of stone. A small museum on site displays a similar model and provides close-ups of the ornately carved stonework used in the slender perforated towers, their upper parts stippled with openings to let out the sound of tubular bells and covered in local trencadís – broken glazed-tile mosaic. Gothic cathedrals seem to point to heaven, but the Sagrada Família leaps out of the ground apparently with the intention of reaching it. While every surface, and particularly those of the three main facades, has some moral to tell or is busy with figures conveying the Christian narrative, there’s no need to be religious to feel uplifted. Organic motifs are omnipresent in the decoration, with an emphasis on species indigenous to Catalonia – palms, snails, shellfish and other sea creatures, as well as a tortoise, turtle and a giant cypress covered in white doves. The creatures on the Nativity Façade, through which visitors enter the building – a donkey, chickens, geese – are as literal as can be, plaster casts having been taken from live creatures. But light was also one of Gaudí’s materials. The use of catenary arches removed the need for the buttresses and load-bearing walls that characterised the often gloomy Gothic, making it possible to line the nave with vast windows. The forest of branching pillars is painted successively in yellows, reds and blues as the day progresses and the sun shines through different areas of stained glass. For now, no one is offering a substitute for the soon-to-be-missed 2026 deadline. But in his time, the pious Gaudí shrugged off criticism of delay. “My client is not in a hurry,” he is said to have remarked.